Add container-native scheduled task system with timezone support

Introduces a cron-based scheduler that lets Claude set up recurring and
one-time tasks inside containers. Tasks run as separate Claude Code agents
and persist across container recreation via the named volume.

New files:
- container/triple-c-scheduler: CLI for add/remove/enable/disable/list/logs/run/notifications
- container/triple-c-task-runner: cron wrapper with flock, logging, notifications, auto-cleanup

Key changes:
- Dockerfile: add cron package and COPY both scripts
- entrypoint.sh: timezone setup, cron daemon, crontab restore, env saving
- container.rs: init=true for zombie reaping, TZ env, scheduler instructions, timezone recreation check
- image.rs: embed scheduler scripts in build context
- app_settings.rs + types.ts: timezone field
- settings_commands.rs: detect_host_timezone via iana-time-zone crate
- SettingsPanel.tsx: timezone input with auto-detection

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/src-tauri/Cargo.toml

@@ -29,6 +29,7 @@ log = "0.4"
 fern = { version = "0.7", features = ["date-based"] }
 tar = "0.4"
 reqwest = { version = "0.12", default-features = false, features = ["json", "rustls-tls"] }
+iana-time-zone = "0.1"
 
 [build-dependencies]
 tauri-build = { version = "2", features = [] }